Should I even build this? Big bore/ Valves/ and S-H cut

[Bub]

Okay,
I'm throwing an engine together "with the parts I have" , I am not trying to build a screamer or anything that rips and goes 60k miles. It's ahodge podge of crap I've collected for fun on a rust bucket 63' ragtop I've resurrected.

Anyway, have a drink and give me an opinion on this-
Using an early 1500 H case (YES, i know...I don't care..lol)
69x87mm
40 x35.5 Valves - with semi/hemi cut
110 Cam
Dual PDSIT from Brazil

I initially was going to run almost 0" deck due to the semi-heads, BUT NOW the piston will touch the step in the heads. I didn't think that through.

Anyways- my 3 scenerios I'm thinking-
1-Swap back to stock bore and run tight deck and more timing
2- shim the cylinders .020" ...will it be a dog? IS it dangerous?
3. cut the step out of the heads and shim to normal .040" 'ish

I don't want it to ping - but just going in a car for messing around, It doesn't need to last forever. I've had the heads forever and they're brand new, and I just forgot about building around stepped heads...haven't done it in so long.

Just cut the heads probably...I know. Nobody in my damn city can flycut a head. Nobody.
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[Dusty1]

Save the single ports!!


Stock bore for 1300 is 77mm. They're the ultimate "thick wall" cylinders and what 1960s VW motors were designed for. That's why every other market aside from the U.S. had 1300s right through the 1970s.

"H" cases used 83mm cylinders for 1500cc.


As a kid I rode a 49cc mini- bike that likely maxed out at less that 5 raging horsepower, later replaced by an 80cc that might have doubled that with a porting job and a pipe.

I remember pawing through the J.C. Whitney catalog as a teenager. OMG! I can build a motor a "lot" bigger than my old 40 horse! 250cc extra is like a Honda Elsinore, extra!

Figure maybe 50 hp / liter for a milder performance VW which works out to 5hp for every 100cc.


I would just as soon build up a single port on my old single port case. Obvious choices are 1300 or 1600cc. 83mm cylinders are scarce.

If you can't find a shop to flycut the heads you'll have no more luck opening up the case.


Track down a set of single port heads and a stock manifold with 30PICT1 carburetor. Bear in mind most of the limited classes in desert raging ran single ports as far back as anyone can remember. Single ports are still the ticket in Class 9 and Class 11.


Save the 110 cam for another day and another motor.


Or...

Throw down a few coins for a used case already opened for 90.5s or 92s easily found in TheSamba Classifieds. Prices are more down to earth now that we're past "supply chain issues".

.
.

[Rome]

If you want to consider Dusty1's suggestions for a single-port 1641 cc engine, your PDSITs can use these intake manifolds- https://www.cbperformance.com/product-p/3261.htm I bought 2 pairs of these manifolds a few years ago from CB as I also have a few sets of Type 3 PDSITS, as well as SP heads. The carb bolt patterns are the same.

[Dusty1]

[Bub]

*crap, had to edit that, I meant 1500, H case, single relief. So the 87's are slip in.

But...I've built engines like this before, in the dirt. And they've actually never failed.

I'm just going to cut the heads, shim to .035" and send it.
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[QRP]

I came across the same issue with deck when I did a sweep the floor 1835cc recently "hateen35"

I chamfered the outer edge of the piston to to match the shape of the chamber to get the min. .040 clearance and ended up with 9.0:1 running a w120

The entire thing was a pile of leftover scraps. 2000 miles so far and it's fun as hell

[Bub]

[Alstrup]

[halfassleatherworks]

It's a hedge podge of crap?


just Shim it so nothing hits put it together, If it is a dog pull the heads and cut out the step and CC the heads and remember to reset the rockers.

[Bub]

[Rome]

OK Bub, with that new strategy for milling the perimeter lip off your dual-port 40 x 35's combustion chambers (noting Alstrup's specific advice), your C35 cam can work reasonably well. But with your calculated 7 CR it'll be very low for that cam.

If your Brazilian PDSITs still have the smallish 24 mm venturies like the later Type 3 ones did, consider upgrading to these 28 mm units- https://www.cbperformance.com/product-p/3296.htm They "should" fit your PDSITs but are cheap enough to experiment. If they work for you, you usually need to increase the main jet size slightly.

Several years ago I bought a pair of 27 mm venturies for PDSIT from aircooled.net, for a set of Type 3 32 PDSITs. The original vendor was not specified. They installed directly into the carb body with minimal modification- on one of the venturi edges there was a protruding small molded-in "nub" which I filed down with a metal file in about 30 seconds' work. I never ran them on an engine.

[Bub]